GDM sometimes not showing device code after selecting broker

I've seen the test case `Test login with GDM` fail after entering the username and selecting the broker. The "Select the broker" UI elements disappear but the device code dialog is not shown:

Observed in:
* https://authd-e2e-test-logs.adrian-dombeck.workers.dev/push-33891271000/run-33891271000-1/resolute-authd-msentraid/log.html#s1-s20-t1
* https://authd-e2e-test-logs.adrian-dombeck.workers.dev/push-34370596846/run-34370596846-1/resolute-authd-msentraid/log.html#s1-s25

Excerpt from the logs of [run-33891271000-1](https://authd-e2e-test-logs.adrian-dombeck.workers.dev/push-33891271000/run-33891271000-1/resolute-authd-msentraid/log.html#s1-s20-t1):

```
Sep 04 16:41:02 ubuntu gdm-session-wor[2965]: Got from GDM: {"type":"pollResponse","pollResponse":[{"type":"brokerSelected","brokerSelected":{"brokerId":"2102147668"}}]}
Sep 04 16:41:02 ubuntu gdm-session-wor[2965]: GDM poll response: type:brokerSelected brokerSelected:{brokerId:"2102147668"}
Sep 04 16:41:02 ubuntu gdm-session-wor[2965]: adapter.brokerSelected{brokerID:"2102147668"}
Sep 04 16:41:02 ubuntu gdm-session-wor[2965]: adapter.BrokerSelected{BrokerID:"2102147668"}
Sep 04 16:41:02 ubuntu gdm-session-wor[2965]: Sending to GDM: {"type":"event","event":{"type":"brokerSelected","brokerSelected":{"brokerId":"2102147668"}}}
Sep 04 16:41:02 ubuntu dbus-daemon[979]: [system] Activating via systemd: service name='com.ubuntu.authd.MSEntraID' unit='snap.authd-msentraid.authd-msentraid.service' requested by ':1.13' (uid=0 pid=1070 comm="/usr/libexec/authd -vv" label="unconfined")
Sep 04 16:41:02 ubuntu gnome-shell[1500]: authd: Broker selected 2102147668
Sep 04 16:41:02 ubuntu gdm-session-wor[2965]: Got from GDM: {"type":"eventAck"}
Sep 04 16:41:02 ubuntu gdm-session-wor[2965]: EventSend&{brokerId:"2102147668"}result
Sep 04 16:41:02 ubuntu systemd[1]: Starting snap.authd-msentraid.authd-msentraid.service - Service for snap application authd-msentraid.authd-msentraid...
Sep 04 16:41:02 ubuntu systemd[1]: tmp-snap\x2dprivate\x2dtmp-snap.rootfs_h6ERoC.mount: Deactivated successfully.
Sep 04 16:41:04 ubuntu authd-msentraid[2996]: Version: 0.4.1+7c091d8
Sep 04 16:41:04 ubuntu authd-msentraid[2996]: Debug mode is enabled
Sep 04 16:41:04 ubuntu dbus-daemon[979]: [system] Successfully activated service 'com.ubuntu.authd.MSEntraID'
Sep 04 16:41:04 ubuntu systemd[1]: Started snap.authd-msentraid.authd-msentraid.service - Service for snap application authd-msentraid.authd-msentraid.
Sep 04 16:41:04 ubuntu authd-msentraid[2996]: Initializing broker for interface com.ubuntu.authd.Broker
Sep 04 16:41:04 ubuntu authd[1070]: Could not parse interface version from "org.freedesktop.DBus.Introspectable"
Sep 04 16:41:04 ubuntu authd-msentraid[2996]: Creating new session (v3) (username=e2e-test@ubudev1.onmicrosoft.com, lang=C, mode=auth, provider_id=)
Sep 04 16:41:04 ubuntu authd-msentraid[2996]: Initializing broker for interface com.ubuntu.authd.Broker2
Sep 04 16:41:04 ubuntu authd-msentraid[2996]: Initializing broker for interface com.ubuntu.authd.Broker3
Sep 04 16:41:04 ubuntu authd-msentraid[2996]: Building new daemon
Sep 04 16:41:04 ubuntu authd-msentraid[2996]: Starting to serve requests
Sep 04 16:41:04 ubuntu authd-msentraid[2996]: Serving requests as com.ubuntu.authd.MSEntraID
Sep 04 16:41:04 ubuntu authd-msentraid[2996]: Created new session cabb117d-bb76-4711-a758-36ed22088119
Sep 04 16:41:04 ubuntu authd[1070]: 2102147668-cabb117d-bb76-4711-a758-36ed22088119: New auth session for "e2e-test@ubudev1.onmicrosoft.com"
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: adapter.SessionStarted{brokerID:"2102147668", sessionID:"2102147668-cabb117d-bb76-4711-a758-36ed22088119", encryptionKey:"MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAyBUpM23d+Irqc4CPLSd5G/FlMdkjN2OTr0Z47J6mHZ+V30WwPDT21oqejcyBt3g8ZIgZOe9MyMl7WH9kRgr2KPJGQ52XWqjIjOwxhAU/usd/BJ1/DwRsgr1/JriNZoPOwaAc7yjFOQ4tkkLnqWCH0q2tAfvnuquD89xQlpEWjMVWEhY3Zz5EvE5joGv2MbZEuTju5wOWTnfRUWg/6zhDOic9pRD+MnrEcBvwa0kuvvQKqAjr6QMpzOaOYsB/DzLa4/Gj+x4/37VDFyEVTZu81bhCynrnev5n0CER4xxKVBQpkXhb97MRkmgEb5po9JBRM51FjyHABsTWwogT+PpTRQIDAQAB"}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: adapter.GetAuthenticationModesRequested{}
Sep 04 16:41:04 ubuntu authd-msentraid[2996]: Getting authentication modes for session cabb117d-bb76-4711-a758-36ed22088119
Sep 04 16:41:04 ubuntu authd-msentraid[2996]: Token does not exist for user "e2e-test@ubudev1.onmicrosoft.com", so local password authentication is not available
Sep 04 16:41:04 ubuntu authd-msentraid[2996]: The "entra_auth" flow is disabled in the [flows] config, so it is not available
Sep 04 16:41:04 ubuntu authd-msentraid[2996]: Got authentication modes for session cabb117d-bb76-4711-a758-36ed22088119: [map[id:device_auth_qr label:Device code flow]]
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: authModes[id:"device_auth_qr" label:"Device code flow"]
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: adapter.authModesReceived{authModes:[]*authd.GAMResponse_AuthenticationMode{(*authd.GAMResponse_AuthenticationMode)(0x3172e9f3e5a0)}}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: adapter.ChangeStage{Stage:"authModeSelection"}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: *adapter.List: Blur
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: adapter.List: Focus
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: Sending to GDM: {"type":"event","event":{"type":"authModesReceived","authModesReceived":{"authModes":[{"id":"device_auth_qr","label":"Device code flow"}]}}}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: adapter.listFocused{id:0x2}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: adapter.listFocused{id:0x2}, autoselect: "device_auth_qr"
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: adapter.StageChanged{Stage:"authModeSelection"}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: Sending to GDM: {"type":"request","request":{"type":"changeStage","changeStage":{"stage":"authModeSelection"}}}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: adapter.authModeSelected{id:"device_auth_qr", fromGDM:false}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: adapter.AuthModeSelected{ID:"device_auth_qr", fromGDM:false}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: Got from GDM: {"type":"eventAck"}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: EventSend&{authModes:{id:"device_auth_qr" label:"Device code flow"}}result
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: Sending to GDM: {"type":"event","event":{"type":"authModeSelected","authModeSelected":{"authModeId":"device_auth_qr"}}}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: Got from GDM: {"type":"eventAck"}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: EventSend&{authModeId:"device_auth_qr"}result
Sep 04 16:41:04 ubuntu authd-msentraid[2996]: Selecting authentication mode device_auth_qr for session cabb117d-bb76-4711-a758-36ed22088119
Sep 04 16:41:04 ubuntu authd-msentraid[2996]: Sending Device Authorization Request to retrieve device code...
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: Got from GDM: {"type":"response","response":{"type":"changeStage","ack":{}}}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: Gdm stage change to authModeSelection sent
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: Got from GDM: {"type":"pollResponse","pollResponse":[{"type":"authModeSelected","authModeSelected":{"authModeId":"device_auth_qr"}}]}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: GDM poll response: type:authModeSelected authModeSelected:{authModeId:"device_auth_qr"}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: Ignoring GDM auth mode selection echo for "device_auth_qr"
Sep 04 16:41:04 ubuntu authd-msentraid[2996]: Retrieved device code. Device Authorization Response: &oauth2.DeviceAuthResponse{DeviceCode:"ABgABIQEAAAA9VeaV3ywaSLp1O3c4_Et5RXZvU3RzQXJ0aWZhY3RzAQAAAAAA9Ov1kX1CX4vVIVieUpLud4XqRkZGIL4jLTNkKsKCpFsIltJ2VeG-nAmThpclGPumqo2h-2fA6UhlDTlQDMssjh3wQ-sL9rRsA3xLI5xlhouAi_y1TlWlR8j08CTDOYue5SmOukVUuGWc6--9qUXVqt_6ZLkjZ3rmjwci4yyfiHwmO3vpVSGrHQaLP1bfrfxsDL2WWsjrGeZuli3obckAlEh5KHgIW3XTsshCiV2bLkHsfQ_I3vADRaYSLCG8qpUQtzhFGNF4jdJnIyhBIJm8R5vo09TS8yicYmiYpfG5yPg83cb22d3BMuAez4eQhXASGxYKQVIm3gbDCipuRhiNBh1DR45acRLc3DTvoPxUYH-b_hpFQiEHR056Fk-a9zg5nTJv8nIJaX5WhEjsVCgZ7hl1HVOnX35QrndFu_YcEs5NKfM9X7hPciQH2AaNeSEIQ0G3jBBkzFntzweZm0pHBuHNxS9sifWnxbpJDu7U6escykUePDo-3DyGRnnI-MAuWkgY961fjYuFtop81k-u0xdst48eUPi990u4I07YvnNHHKUpmBuHVaK2V8IcRKQHfO3eWriLBuniTkewYvQTvlKiGsUCUw9IoF3-KVL50MeB7K_eXFCi6eXFPZV1-WWvCNbSHrPWIPN1hZsRJQj51C7pBuGqkQAeeSXpgWIun-gJ30UOBk80j4YqvSXz7qDTov-P_RkMic_8nrtw3qv80ow0G-c4w8G78my_z7lCNF4gAA", UserCode:"AE3P6KPNN", VerificationURI:"https://login.microsoft.com/device", VerificationURIComplete:"", Expiry:time.Date(2026, time.September, 4, 16, 56, 4, 676640437, time.UTC), Interval:5}
Sep 04 16:41:04 ubuntu authd-msentraid[2996]: Selected authentication mode device_auth_qr for session cabb117d-bb76-4711-a758-36ed22088119: map[button:Request new code code:AE3P6KPNN content:https://login.microsoft.com/device label:Scan the QR code or open the URL and enter the code below. type:qrcode wait:true]
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: adapter.UILayoutReceived{&authd.UILayout{state:impl.MessageState{NoUnkeyedLiterals:pragma.NoUnkeyedLiterals{}, DoNotCompare:pragma.DoNotCompare{}, DoNotCopy:pragma.DoNotCopy{}, atomicMessageInfo:(*impl.MessageInfo)(nil)}, Type:"qrcode", Label:(*string)(0x3172ea0f04b0), Button:(*string)(0x3172ea0f04c0), Wait:(*string)(0x3172ea0f04d0), Entry:(*string)(0x3172ea0f04e0), Content:(*string)(0x3172ea0f04f0), Code:(*string)(0x3172ea0f0500), RendersQrcode:(*bool)(nil), unknownFields:[]uint8(nil), sizeCache:0}}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: Sending to GDM: {"type":"event","event":{"type":"uiLayoutReceived","uiLayoutReceived":{"uiLayout":{"type":"qrcode","label":"Scan the QR code or open the URL and enter the code below.","button":"Request new code","wait":"true","entry":"","content":"https://login.microsoft.com/device","code":"AE3P6KPNN"}}}}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: Got from GDM: {"type":"eventAck"}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: EventSend&{uiLayout:{type:"qrcode" label:"Scan the QR code or open the URL and enter the code below." button:"Request new code" wait:"true" entry:"" content:"https://login.microsoft.com/device" code:"AE3P6KPNN"}}result
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: adapter.ChangeStage{Stage:"challenge"}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: *adapter.List: Blur
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: adapter.authenticationModel: Focus, focused false
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: *adapter.focusTrackerModel: Focus
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: adapter.StageChanged{Stage:"challenge"}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: adapter.StageChanged{Stage:"challenge"}, in progress false, focused: true
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: Sending to GDM: {"type":"request","request":{"type":"changeStage","changeStage":{"stage":"challenge"}}}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: adapter.startAuthentication{}, current model &{true}, focused true
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: Sending to GDM: {"type":"event","event":{"type":"startAuthentication","startAuthentication":{}}}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: Got from GDM: {"type":"response","response":{"type":"changeStage","ack":{}}}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: Gdm stage change to challenge sent
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: Got from GDM: {"type":"eventAck"}
Sep 04 16:41:04 ubuntu gdm-session-wor[2965]: EventSend&{}result
```

Maybe the `Could not parse interface version from "org.freedesktop.DBus.Introspectable"` is the issue?

Edit: The `Could not parse interface version from "org.freedesktop.DBus.Introspectable"` warning is apparently always printed and has nothing to do with the issue.

Start by reproducing the `Test login with GDM` case and compare the linked end-to-end logs around broker selection, authentication-mode selection, and the `uiLayoutReceived` event. Trace why the device-code dialog is not displayed after the broker is selected; done means the test reliably shows the device-code dialog and the persistent DBus warning is not treated as the cause.

Written by the indexing model from the issue text.